Known technologies for controlling access (writing of data to) memory devices include a technology whereby a device for preventing write operations to a memory device is grounded outside the memory device. In another known technology, information disallowing write operations to a data memory area is written to an address after the data memory area, thereby prohibiting further write operations to the data memory area.
However, where a device for preventing write operations is provided outside the memory device, it was necessary to provide the external write prevention device in addition to the memory device. In technology permitting settings to be made to enable or disable access to data memory areas, some time is needed for the determination as to whether writing to a data memory area is enabled or disabled, and there was always the risk that a data memory area might be written to inadvertently during the write enable/disable determination process. There was also the risk that settings prohibiting access to an entire data memory area of a memory device might not be made appropriately.